If you're looking for less complications, the modular can be both an asset or a curse. It can be bad as you will have to know what cables go where when plugging them into the PSU (which really isn't bad) but it can also be awesome as you are then only sitting with cables you're going to use and you can forget about the ones that aren't, you don't have to search for space to hide them away in the case.
Also remember that the PSU's you mentioned here are quite large, and they may very well be too large. You can build a massive PC with two GTX570's in there with the PSU's you mentioned. Post your prospective specs to let the guys here help you choose to ensure you're not wasting money on unneeded power.
Thanks for your swift reply. Specs are posted here in the New Build forum. I want to go with a 750w unit so I can have upgradability to a dual GPU in a couple months. I'd hate to buy a 650w to save a few dollars now and then find out it won't be enough later.
For the 6870's the 750W PSU is perfect. Just one question - why pick the 6870's over the GTX560 Ti's? They scale incredibly well, you know...
The choice was mainly an issue of a $30-40 difference for an EVGA or similar MSI card, but that was my 1st choice however. Hence my question about the value of a modular PSU. I'm still working on trimming the fat off the system to stay within budget and put the savings into one of these cards.
Here's the other thing to consider:
If you do run with 2 video cards, you will not have many cables left over. At that point, modular cables are a nearly useless expense.
And depending on your case, you should have plenty of room to hide the unused cables.
I drilled extra holes in the bottom of my cases (Antec 900's) and secured the unused cables with nylon cable ties. The unused cables are out of the way, nearly invisible in the side window, and they are available if I need one of them later.